Video magnifiers are important tools for individuals who are blind or have low vision (i.e.“BLV users”). The construction typically includes an arm mounted camera and an associated monitor. The arm allows the camera to be directly positioned over the object being viewed. The object may be, for example, a prescription pill bottle or a newspaper or book. The arm is usually adjustable to permit the camera to focus upon a particular portion of the object or document. BLV users can then select a desired level of magnification so that the object, and any associated text, can be sufficiently enlarged for viewing and reading. Color contrasting and image rotation can be provided to further ease viewing. An X-Y table can optionally be positioned beneath the camera to allow for precise movements to the object being viewed. A video processor and look up tables are used to process the video signal generated by the camera. The video signal can be processed to make changes to one or more of the following: image scale; image position; color contrast; as well as other image features.
For all of these reasons, video magnifiers have become an indispensable tool to members of the BLV community. Nonetheless, traditional video magnifiers still suffer from some shortcomings. One of these shortcomings is latency. Latency refers to the slight delay that results from the video signal being processed. This delay is usually measured in milliseconds and occurs between the image being captured by the camera and its subsequent display upon the monitor. The use of frame buffers generally increases latency. Frame buffers are memory stores that contain a bitmap of an entire frame of data. Frame buffers allow the video frame to be scaled and otherwise allows desired attributes to be applied to the frame. The latency that results from frame buffering is largely unnoticeable in most applications. However, latency is highly problematic in the context of a video magnifier, as BLV users will notice a lag between the manipulation an object and its subsequent appearance on the video monitor. This lag greatly complicates the manual tasks performed by BLV users.
Known video processing systems typically require multiple frame buffers. In a typical video processing system there are three frame buffers, one to store the incoming frame, one to store the frame that is being manipulated in memory, and one to store the output frame. In a low-vision magnification system, there can be many design blocks, which each adding more frame buffers. The cumulative total of frame buffers times the frame time results in a large delay between an event in front of the camera and when it appears on the display. This delay or video latency causes significant problems for low vision users when they attempt tasks in front of the camera that require eye-hand coordination. Examples include writing during test taking, signing a name to a document, or attempting to push a needle through fabric while sewing. Every frame buffer adds to the cumulative photon to photon latency, which can be measured on a black box system by triggering a bright point source of light in front of the camera system and them measuring the delta in time to when the light is visible on a monitor.
Video magnifiers also employ techniques to help focus the user's vision upon the screen. For this reason, traditional video magnifiers sometimes black out regions of the screen. The blacked out regions tend to highlight the non-blacked out regions. This allows the BLV user to focus upon one area of an object. In the case of text, it allows the BLV user to read one line of text at a time. The underlying text may be scrolled so that sequential lines are presented to the user.
Masks have long been used in security systems to block areas in a scene that require privacy, such as the windows of an apartment building. The mask's objective is to obliterate or obfuscate the area that should be kept confidential in the scene. In security cameras with PTZ (pan-tilt-zoom), the mask is typically maintained over the protected area of the scene as the camera aim is changed. UK Patent Application GB 2,472,307 discloses a document camera presentation device with markers placed on the document to mask selected areas. Although this technique is beneficial, it has some drawbacks. By blacking out regions of text, the BLV user often loses their place within the document. It also makes it difficult for the user to navigate around an object and through lengthy text.
In a low-vision system, the purpose of the mask is to reduce the integral of light entering the user's eyes. Many low-vision users are sensitive to light and develop eye-strain when using a bright monitor. The masks in a low-vision magnifier are typically placed at the top and bottom of the display output, irrespective of the input scene. This leaves a wide central region where magnified items, typically written words, are visible. In the past users would cut up card board boxes and tape them to their monitors to block off a large percent of the display to help reduce eye-strain from too much light. This method gave rise to the digital horizontal and vertical masks now used in many low-vision magnifier systems. While masks solve the problem of too much light entering the user's eyes they created a new problem, where the user's field of view became substantially limited, making the user lose their spatial perspective in the document or scene they were trying to observe during eye-hand coordinated tasks.
Various video processing techniques are known in the prior art. Some of these techniques discuss reducing latency. For example, WO2013/068584 to Eaturnus discloses a ultra-low latency video communication system. This system employs a transmission unit with image acquiring circuitry or image reconstruction circuitry for acquiring or reconstructing an image frame or an image field. A video processing unit is also included for processing at least part of the video data. Also included is a communication unit for sending or receiving at least part of the video data.
Similarly, US Pub 2005/0288932 to Kurzweil discloses a system for reducing processing latency in optical character recognition for a portable reading device. The portable reading device may include a computing device with a computer readable medium for storing a computer program to receive an image and select a portion of the image to process. The device then processes the selection of the image with a first process, and when the first process is finished, a second process is initiated. While the second processing, the first process is repeated on another section of the image.
US Pub 2013/0329114 to Kim discloses an image magnifier with point control. The method allows for image control using magnification. The method comprises selecting a portion of the image, and then magnifying the selected portion. An action is then performed on the magnified and selected portion of the frame. The change may involve changing a feature of the selected portion.
Although these inventions achieve their own unique individual objectives, all suffer from drawbacks. For example, none of the prior art sufficiently eliminates the problems associated with latency. Likewise, none of the prior art allows shading to be applied to selected portions of a document in a manner suitable by low vision users.
What is needed, therefore, is a desktop video magnifier camera includes a pass through signal processor that eliminates the use of frame buffers and that greatly reduces associated latency. The video magnifier of the present disclosure is designed to fulfill this and other shortcomings present with existing video magnifiers.
What is also needed is a magnifier camera that allows portions of an object to be viewable but shaded. This would allow select portions of an object or text to be highlighted while at the same time allowing the remainder of the object or text to be perceived. The video magnifier of the present disclosure is designed to fulfill this and other shortcomings present with existing video magnifiers.